Volume 15 Issue 2

To explore the extensive oxidative mechanism of syringaldehyde, vanillin, and p-hydroxybenzaldehyde during the alkaline wet oxidation process (AWOP), the yield of these aromatic aldehydes from AWOP at various temperatures and reaction times was studied. The results showed that the aromatic aldehydes could not be converted into the corresponding aromatic acids during the AWOP, and that the aromatic aldehyde was stable when subjected to the oxygen-free AWOP. However, as the reaction temperature increased or the number of methoxyl groups on the aromatic ring increased, the yield of aromatic aldehyde sharply decreased during the AWOP. The reason for the decreased yield was that the aromatic aldehyde underwent ring-opening reactions. The possible mechanism of the degradation indicated that the number of methoxyl groups on the phenolic ring determined the stability of the key intermediate of this reaction. The conversion of isoeugenol to vanillin during the AWOP at 60 ºC was > 99%, and the vanillin yield and selectivity were both 69.8%, indicating that the decrease in yield of the product from this degradation of lignin substrate and the product can be reduced or avoided in the AWOP at suitable temperature.

Pseudo-static tests of a novel energy-dissipation connection, comprised of a hinge and two steel brackets, have proven their reliability and superior energy-dissipation capability. To verify the effectiveness of the connection further, a full-scale one-story one-bay engineered bamboo-steel hybrid frame jointed with the novel energy-dissipation connections was investigated through experimental test and finite element analysis (FEA) in this paper. The experimental results showed that the failure mode of the frame was restricted in the local buckling of the energy-dissipation panels (EDPs) in the innovative connections, whereas no obvious damage was observed in the other components of the frame. The hysteresis loops of the frame with energy dissipation connections revealed less pinching. Thus, the ductility and damping ratio of the engineered bamboo-steel frame can reach 1.46 and 14.1%, respectively. Based on the analysis of effectual simulation models in ABAQUS software, the relationship between the initial stiffness, the peak load, the ductility ratio of the hybrid frame and the size of EDP was studied. Recommendations are made for the design of the EDPs.

Rapid qualitative analysis was used to determine the influence of the lignin content of wood cell walls on the compression and bending properties of multiple wood species. The lignin type and cell wall content of Cunninghamia lanceolate, Fagus longipetiolata, Betula alnoides, Fraxinus mandshurica, and Tectona grandis was analyzed via histochemical staining, which included: the Mäule staining reaction, the Weisner staining reaction, and a fluorescence reaction. The results showed that the more red the Mäule staining reaction was, the greater the Syringyl lignin (S-type lignin) content was, and the more yellowish-brown the Mäule staining reaction was, the greater the Guaiacyl lignin (G-type lignin) content was. In addition, the more reddish-purple the Wiesner staining reaction was, the greater the lignin content was. The greater the brightness value of the fluorescence reaction was, the greater the lignin content was. Due to the negative correlation between the lignin content of the wood cell wall and the bending and compression properties of the wood, the application of histochemical stains for the analysis of wood lignin content could provide a reference and experimental basis for bending and compression treatments of various woods.

The bonding performance of the phenol-resorcinol-formaldehyde adhesive (PRF) and melamine-urea-formaldehyde adhesive (MUF) with southern pine as substrates at various moisture contents (MC) was evaluated. The results showed that bonding shear strength with MUF and PRF was negatively related to wood MC, and bonding shear strength with MUF was higher than that of the PRF. The bending and tensile strengths of finger-jointed lumber decreased with wood MC. The bending strength of finger-jointed lumber was affected more by wood than adhesive. However, both wood and adhesive exhibited the same important contribution to the tensile strength.

Phytoremediation of metal-contaminated soil can be an eco-friendly technology. However, relatively long cultivation times impedes its popularization on a commercial scale. This study evaluated the effectiveness of lavender plants (Lavandula dentata L.) to remediate a highly chromium (Cr)-contaminated site through a pot experiment. The lavender growing soil was mixed both with and without biochar (2.5% w/w) + oyster shell waste (2.5% w/w) and biochar (2.5% w/w) + citrus peel waste (2.5% w/w). The results indicated that Cr(VI) accounted for 19.0% to 4.7% of the total soil Cr, while Cr(III) accounted for 81.0% to 95.3%, from the beginning to the end of the cultivation. The water-soluble Cr concentration decreased from 44.6 mg/kg to 7.5 mg/kg. The biomass of the lavender growing in the contaminated soil decreased by factors in the range between 4-fold and 6-found.The addition of soil amendments significantly reduced the (potential) bioavailable Cr (p < 0.05) in the range of 2 to 3 fold, consequently improving the growth of lavender in the highly toxic soil. In addition, the soil amendments significantly reduced the Cr bioaccumulation and the translocation from the roots to the shoots. These results showed that the cultivation of lavender with suitable amendments can effectively be used for phytomanagement techniques in highly contaminated soil.

Wood fiber was modified by impulse-cyclone drying treatment with poplar and montmorillonite as reinforcing materials; mMMT/polypropylene/wood fiber foaming composite was prepared by the hot compression process. The effects of modification, temperature, and content of montmorillonite on physical and mechanical properties of the composite were analyzed. Mechanical properties, porosity, shrinkage, water absorption, and thickness swelling tests showed that when mMMT reinforcement was 5 wt%, the best performance was achieved. The scanning electron microscopy observations showed that bubble holes were distributed widely and evenly, and mMMT appeared in the cell gap and was encapsulated by polypropylene, which maximized the bonding effect. Flexural strength was 27.5 MPa, flexural modulus was 2110 MPa, tensile strength was 20.0 MPa, and impact strength was 6.30 KJ/m2. When absolute volume of dense solid reached 70.8 cm3, porosity was 21.4% and shrinkage was 1.17%, which indicated that the water absorption increased most remarkably under that test condition. When equilibrium water absorption reached 9.28%, the thickness swelling decreased by 25%. The results showed that mMMT effectively optimized mechanical properties of wood-based foamed composites and improved hygroscopic properties.

The deterioration of insulation pressboard under needle-plate discharge was tested, and the degradation stage was divided according to observed experimental phenomena. Based on the improved Top-hat watershed image segmentation method, the white marks area of the pressboard were tested. Fibres with different discharge states were extracted from SEM images. The fibre width was calculated, and the porosity of the surface of the insulation pressboard at different degradation stages was calculated. Simultaneously, the 3D reconstruction technique was used to observe the 3D morphology of fibres at different discharge stages. The study found that with the deepening of the discharge process, the discharge of the pressboard increased, and the white marks of the pressboard continued to expand from point to surface. In addition, the diameter of the fibre of the insulating pressboard decreased obviously with the increase of the pressing time, and the fibre diameter was 89.6% after the breakdown. Moreover, the electrical stress had a great effect on the expansion of the interlayer pores of the pressboard; the cross-section porosity of the insulating pressboard gradually increased with the deepening of the discharge process, and after breakdown, the interlayer porosity reached 12.5%.

Chemical and thermal aspects of Pinus sylvestris and Pinus pinaster were characterized, with consideration of non-extracted and cylohexane-ethanol (EtOH)-extracted woods, holocellulose, and α-cellulose. The chemical properties including cylohexane-EtOH solubility of wood were determined by standard test methods, holocellulose, α-cellulose, lignin, and ash components. Fourier transform infrared–attenuated total reflection spectroscopic (FTIR-ATR) analysis revealed changes in the chemical structure of the specimens. Lignin peaks were still observed in holocelluloses’ spectra, and substantial loss of polysaccharides were also detected. Moreover, the α-cellulose spectra of both softwoods included bands belonging to polyoses. Pinus pinaster‘s holocellulose, α-cellulose, and ash contents were higher than those of Pinus sylvestris but lignin and cylohexane-EtOH-solubility amounts were lower. The mass loss during degradation stage of Pinus sylvestris and Pinus pinaster was observed in the extracted wood respectively as 73.0 and 74.5% within the 188.7 to 422.9 °C range. The highest mass loss for Pinus sylvestris and Pinus pinaster in the carbonization step was formed in their holocelluloses respectively as 22.9 and 22.5% from 426 °C to 1017 °C.

5-Ethoxymethylfurfural (EMF) is a new type of biofuel with a high energy density and excellent fuel properties. One-pot production of EMF from renewable carbohydrate catalyzed by heterogeneous catalysts has the potential to be an attractive reaction pathway. In this study, fructose was directly converted to EMF in ethanol medium catalyzed by ultra stable Y zeolite (USY). The effects of different reaction conditions on EMF yields were investigated, and an optimum reaction condition was obtained by utilizing response surface methodology. Under the optimum reaction conditions, which were a temperature of 132 °C, substrate density of 60 g/L, and catalyst dosage of 2.1 wt%, a maximum EMF yield of 73.8 mol% with the prediction error of 1.6% was achieved in 25 min. Moreover, the reusability of USY and characterization were evaluated. This study demonstrated a promising strategy for EMF production from fructose.

The effects of three different pretreatments (H2SO4-heat, NaOH-heat, and hydrothermal pretreatment) on the enzymatic hydrolysis efficiency of Sophora flavescens residues (SFRs) were studied. After NaOH-heat pretreatment, the cellulose content of SFRs increased from 46.6% to 59.4%, and hydrolysis efficiency was 2.3 times higher than that of direct enzymatic hydrolysis without pretreatment. Moreover, the optimum pretreatment conditions were NaOH concentration of 1.00%, solid-liquid ratio of 1:10, temperature of 80 °C, and pretreatment time of 60 min. Under these conditions, 85.0% hydrolysis efficiency was obtained. When SFRs with NaOH-heat pretreatment were used as feedstocks in fermentation, the maximum lactic acid concentration was 33.7 g/L, which was twice that produced by SFRs without pretreatment. Mechanism analysis suggested that the lignin of SFRs was removed by NaOH solution, and the deacetylation reaction of hemicellulose occurred, which made the original smooth and dense structure become rough and loose, thus improving the accessibility of cellulose to enzymes.